Inductive, Deductive Reasoning ผศ.( พิเศษ ) น. พ. นภดล สุชาติ พ. บ. M.P.H.

Inductive and Deductive Reasoning Many people distinguish between two basic kinds of argument: inductive and deductive.

Induction Induction is usually described as moving from the specific to the general, arguments based on experience or observation are best expressed inductively, Induction Specific  General เริ่มต้นจาก ประสบการณ์ หรือจาก การสังเกต เป็น inductive

Deduction while deduction begins with the general and ends with the specific while arguments based on laws, rules, or other widely accepted principles are best expressed deductively Deduction General  specific เริ่มต้นจาก กฎ หรือ หลักวิชา ก่อนแล้ว สรุปผล เรียก deductive

Inductive Reasoning Consider the following example: Adham: I've noticed previously that every time I kick a ball up, it comes back down, so I guess this next time when I kick it up, it will come back down, too. ทุกครั้งที่เตะลูกบอล ขึ้นไปลูกบอลจะตก ลงมาดังนั้น คาดว่า ครั้งต่อไปถ้าเตะลูก บอลขึ้นไปอีกลูก บอลก็คงจะตกลงมา อีกเหมือนเดิม ( เคยทำครั้งที่ 1 มาแล้วจึงคาดคะเน ผลครั้งที่ 2)

Deductive Reasoning Rizik: That's Newton's Law. Everything that goes up must come down. And so, if you kick the ball up, it must come down. กฎของนิวตัน ทุก อย่างที่นำไปไว้อยู่ บนที่สูงจะตกลงมา ที่พื้น ดังนั้นถ้าคุณ เตะลูกบอลขึ้นไปลูก บอลคงจะต้องตกลง มา ( แม้ว่าจะไม่เคย ทดลองทำแม้แต่ ครั้งเดียว )

Adham is using inductive reasoning, arguing from observation, while Rizik is using deductive reasoning, arguing from the law of gravity.

Rizik's argument is clearly from the general (the law of gravity) to the specific (this kick); Adham's argument may be less obviously from the specific (each individual instance in which he has observed balls being kicked up and coming back down) to the general (the prediction that a similar event will result in a similar outcome in the future) because he has stated it in terms only of the next similar event--the next time he kicks the ball.

As you can see, the difference between inductive and deducative reasoning is mostly in the way the arguments are expressed. Any inductive argument can also be expressed deductively, and any deductive argument can also be expressed inductively.

Even so, it is important to recognize whether the form of an argument is inductive or deductive, because each requires different sorts of support.

Adham's inductive argument, above, is supported by his previous observations, while Rizik's deductive argument is supported by his reference to the law of gravity. Thus, Adham could provide additional support by detailing those observations, without any recourse to books or theories of physics, while Rizik could provide additional support by discussing Newton's law, even if Rizik himself had never seen a ball kicked.

The appropriate selection of an inductive or deductive format for a specific first steps toward sound argumentation

References /induc/ind-ded.html